This invention relates to electric heating cable suitable for use in electric heating appliances.
French publication (2,611,106) describes a heating element formed from linearly juxtaposed heating wires linked together to form a single wire in a series circuit loop. The two wires are placed side by side and carry equal current in opposite directions such that the resulting magnetic field produced by the wires is reduced.
Watson (U.S. Pat. No. 3,356,835) describes a heating wire which is effectively shielded from damage, abrasion, nicks and cuts.
Weckstein (U.S. Pat. No. 3,859,506) describes a constant wattage heating element in which a conductor rod is enclosed by a tube of electrically insulating material which in turn is enclosed by a tubular conductor. Discrete resistors are provided in the tubular insulator so that the heating element has a constant wattage per unit length.
Wringer et al. (U.S. Pat. No. 3,492,463) describe an electric resistance heater constructed by shrinking a tubular metal jacket about a rod of electrically insulating material, such as boron nitride or berillium oxide, and then shrinking the tube about a rod-shaped or tube shaped resistance conductor, constructed of molybdenum, tantalum, columbium or alloys thereof.
Kishimoto (U.S. Pat. No. 4,698,488), Kishimoto et al. (U.S. Pat. No. 4,792,663) and Farkas (U.S. Pat. No. 4,200,973) describe various flexible thermosensitive wire arrangements suitable for use as self-temperature regulating electric heating cable. In these cables, a pair of electrodes are provided, separated by a semiconductive composition. The temperature of the composition determines its resistance and the current flowing through it. This in turn determines the amount of heat produced at any point in the wire.